Toothbrushes are well known articles generally comprising a head for insertion in the user's mouth and a grip handle to be held by the user during use. Toothbrushes may be manual toothbrushes in which the head is moved within the user's mouth in contact with the user's teeth by hand action applied to the handle, or power toothbrushes in which the handle incorporates a motor by means of which the head is moved. The toothbrush head normally has a surface, termed herein the “bristle surface” from which plural tufts of bristles extend in a bristle direction.
Toothbrush bristles are well known to consist of fine filaments comprised of one or more polymer material. A variety of types of toothbrush bristles are known.
The most common type of bristle is a unitary filament i.e. made of a single polymer material, typically polyamide (e.g. nylon such as Nylon 6.12) such as the bristle material Tynex™, polybutylene terephthalate (PBT) or polyethylene terephthalate (PET), of generally uniform circular cross-section and normally being end-rounded, i.e. having its end remote from the bristle surface rounded to prevent damage to the soft mouth tissues such as the gums.
Another type is a so-called tapered bristle comprising a filament, usually a unitary filament, which tapers toward its end remote from the bristle surface in a conical sloping profile over a substantial part of its length remote from the bristle face, e.g. 10-50% of its length remote from the bristle surface to a sharp point. The term “tapered bristles” is a term of the toothbrush bristle art, a synonym being “pointed bristles” as for example used in US-A-2006/0096053, or “needle shaped bristles” as for example used in EP-A-1 425 989. For example such tapered bristles are disclosed in EP-A-1 234 525, EP-A-1 415 572, U.S. Pat. No. 6,546,586, WO-A-97/42853, WO-A-97/42854, WO-A-01/32053, WO-A-82741, EP-A-0 596 633 among others. Tapered bristles, being thinner at their upper pointed end, have different bending and flexibility characteristics to non-tapered filaments. Tapered bristles are generally more flexible than non-tapered bristles of the same cylindrical diameter. In particular tapered bristles are known for efficacy in reaching into the spaces between the teeth, the so called “interproximal” spaces. Typically, tapered bristles may be made of polyamide (nylon such as Nylon 6.12), or polyester such as polybutylene terephthalate (PBT) or polyethylene terephthalate (PET). Two types of such tapered bristles are used, one type being mechanically tapered in which the ends of the filaments are mechanically ground to a point, and another type being chemically tapered in which the ends of the filaments are chemically eroded to a point. As disclosed for example in U.S. Pat. No. 6,090,488 PBT and PET bristles are preferably eroded chemically to a tapered end. Chemically tapered bristles normally taper to a finer point than mechanically tapered bristles.
It is known to combine tapering and non-tapering bristles on a toothbrush head. For example U.S. Pat. No. 6,546,586, US-A-2006/0096053, U.S. Pat. No. 3,103,679, US-A-2008/0271276, WO-A-96/16571 and DE-A-35 28 596 among others disclose toothbrush heads in which each tuft comprises plural bristle filaments in the form of shorter filaments of uniform cross section and longer filaments which taper toward their upper end.
Another type of bristle is a so-called co-extruded bristle comprising a filament made of two different polymer materials. These different polymer materials may be arranged as a core and outer, e.g. concentric, sheath formed respectively of these different materials. Examples of such co-extruded bristles are disclosed in WO-A-97/14830 and WO-A-98/26117. A particular type of such co-extruded bristles disclosed in WO-A-99/24649 (Pedex) has a core of one material such as a polyolefin, particularly a thermoplastic elastomer (TPE), and a sheath made of PBT or polyamide. Typical such materials are a core of Hytrel 8238 thermoplastic elastomer and an outer sheath of Ultradur B4500 PBT. In one commercially available (e.g. from Pedex GmbH) form of such coextruded bristles the core extends to the outer surface of the sheath at one or more place around the perimeter of the bristle, and in one such form the polyolefin core is cross-shaped, with segments of the sheath material between the arms of the cross, and the ends of the arms of the cross being exposed at the outer surface of the filaments.
Typically toothbrush bristle filaments are circular in cross section with a diameter ranging between about 0.18 mm for soft bristles, through about 0.3 mm for medium bristles, to ca. 0.36 mm for hard bristles. Typically toothbrush bristles are arranged on a toothbrush head in tufts of a generally circular cross section, typically ca. 1.0-1.5 mm diameter.
It is an object of this invention to provide an improved toothbrush head incorporating combinations of different types of bristles, particularly end-rounded, tapered and co-extruded bristles, for example providing improved tooth cleaning, particularly in the interproximal spaces, at the gingival margin and in subgingival areas. Other objects and advantages of the invention will be apparent from the following description.